Seizing the Enigma: The Race to Break the German U-Boat Codes, 1933-1945

by Kahn, David

  Turing and Twinn came to me like undertakers cheated of a nice corpse two days ago, all in a stew about the cancellation of Operation Ruthless. The burden of their song was the importance of a pinch. Did the authorities realise that … there was very little hope, if any, of their deciphering current, or even approximately current, Enigma … at all.

  Fleming replied that the value of a pinch was fully recognized and that RUTHLESS was still fully laid on. The navy awaited favorable circumstances. But they never materialized, and the plan faded away.

  Thus the crisis with the naval Enigma continued. Pressure on the cryptanalysts increased. Churchill told the Commons on November 4, 1940, that “the recent recrudescence of U-boat sinkings in the Atlantic approaches to our islands” was “more serious than the air raids” of the Blitz. That same month, banana imports were stopped; the next month, the meat ration was ordered reduced. No cryptanalyst could envision a way of cracking the naval Enigma and reading the U-boat messages so as to steer the convoys bringing supplies to Britain out of harm’s way.

  Still, though Hut 8 had had little success throughout 1940, and despite the increasing strain, the atmosphere in the group was not disheartened but industrious. Then, early in 1941, another clue to the naval Enigma arrived, as tantalizing as it was helpful.

  10

  IN THE LOCKED DRAWER OF THE KREBS

  THE CENTRAL ACTOR WAS A BLUE-EYED BARONET, LIEUTENANT Sir Marshall George Clitheroe Warmington, signals officer aboard the destroyer Somali. The son and grandson of London barristers, Warmington had been brought up in Great Missenden, Buckinghamshire, and educated at Charterhouse, one of England’s better public schools. He wanted to join the cavalry, but his father vetoed that, and in 1928 he found himself in the Navy on the H.M.S. Erebus, a training ship. Warmington felt that this converted World War I monitor exceeded its name by being not just an anteroom to hell but hell itself. The future officers ate and slept and worked in a gunroom in which they couldn’t stand upright. When the showers were working, they either scalded or froze those standing under them. Though the Erebus was docked at Devonport, the men were allowed ashore only twice a week, and then they had to be back by 7:30 P.M. The experience was rather squalid, but it was apt: the whole Navy, Warmington thought later, was rather squalid at the time.

  This inauguration was followed by tours in the Mediterranean and in the Home Fleet, by study at Greenwich and Portsmouth, and then by long months of patrol under the broiling Red Sea sun. His ships, the Penzance and the Hastings, were supposed to be stopping the Arab slave trade, but they never did: the slave traders simply avoided them. Their real purpose was to show the flag. So the ships sailed from Aden near the mouth of the Red Sea to Malta in the middle of the Mediterranean, calling at Jedda and Port Sudan, nosing into the Gulf of Aqaba, passing British and French Somaliland. The tedium of idleness and of four-hour watches on the bridge was broken only by a bit of gunnery practice and some fishing from the motorboat. In August 1935, upon his father’s death, Warmington succeeded him as third baronet, becoming a member of the lowest hereditary order, whose members, not peers, are addressed in society as “Sir.” In the navy, however, all of the officers addressed one another by last name alone.

  In December 1935, Warmington returned to Portsmouth for a year-long course in communications, or signals, as the Royal Navy called it. He liked the field, but the course was “jolly hard work”: Morse code training twice each day to reach at least twenty-five words per minute, visual flag signals, wireless technique and technology, the communications aspects of maneuvering the fleet, codes and ciphers. Warmington then served for a couple of years as a signals officer for a submarine flotilla. After the war began, he was transferred to the staff of the forces that helped evacuate the tattered British forces from Dunkirk after Hitler’s blitzkrieg smashed France. Then, to his pleasure, he was assigned to the Somali.

  She was a member of the newest, largest class of destroyers in the Royal Navy. Earlier classes had been small, handy vessels with good torpedo armament, but the building by Italy and Japan of large fast destroyers with heavy gun armament, and indications that Germany might do the same, led the Admiralty to design a counterforce. The new ships, almost half again as big as the older ones, would double the number of the older classes’ guns but halve their torpedo armament—a revolutionary design that some criticized as being more like that of a small cruiser than of a big destroyer. When a drawing was submitted to the Board of Admiralty for approval, one of the sea lords criticized the straight stem and penciled in a slight curve. This “proud nostril curve” in the profile of the bow distinguished the new class, which was called Tribal because its members bore the names of native tribes, many of the British Empire: Zulu, Ashanti, Sikh, Cossack, Tartar, Maori.

  The keels of six Tribals were laid down in 1936. They displaced 1,959 tons and carried eight 4.7-inch guns, each of which hurled a 50-pound shell 10 miles, and four torpedoes in tubes. The vessels were not armored. Their speed was excellent, a little above 35 knots. The normal wartime complement was around 220, but some Tribals were fitted out as flotilla leaders with accommodations for the additional men and officers needed to command the eight vessels.

  One such leader was the Somali, named for the Hamitic herders and fisher folk of the Horn of Africa. Launched in August 1938, the Somali was the first Home Fleet Tribal to be completed. After the others were commissioned, the Somali’s captain became the leader of the Home Fleet’s Sixth Destroyer Flotilla; in Royal Navy parlance he was the “Captain (D).” The Somali became the first Royal Navy vessel to capture a prize at sea in World War II when, two hours after war was declared, she seized the Hannah B? of Hamburg, which was carrying wood pulp from Canada. Later she engaged in operations in Norwegian waters, including the bombardment of Narvik. Soon thereafter Warmington joined the crew.

  During the winter of 1940–41 some days were spent in practice with the guns or with the asdic gear for detecting and locating submarines or in antisubmarine exercises. Other days the destroyers screened heavier warships that were searching for a German raider or merchantman. Lookouts on both sides of the bridge scanned the horizon through their heavy 8 × 41 binoculars for five minutes, then were relieved by others for five minutes, and so on for one hour, after which both pairs were relieved. Visibility was often poor: during one five-day period the lookouts could see more than 10 miles for a total of only five hours. Many times, fog and mist reduced visibility to a mile or less. The strain, the chill of the North Atlantic, the days of four-hour watches, the wet—all wearied the men. But in some rare but lovely moments, the sea was calm and moonlit, and the lookouts could see out to the very rim of the horizon.

  Then, early in 1941, orders came that broke the tiresome routine of training exercises and North Sea sweeps. The Somali was going to lead four other Tribals and two troop carriers on a commando raid on German-occupied Norway.

  The raid had several specific objectives. One was to destroy herring-and cod-oil factories that were providing the Germans with valuable nutrients, in particular vitamin A, it was said. Another was to perfect interservice cooperation in amphibious operations. Still other objectives were to arrest quislings (Norwegians collaborating with the occupiers), capture Germans, and evacuate Norwegians who wanted to fight for the Norwegian government in exile in London. An important purpose was to tie down large enemy forces by keeping realistic the threat of attacks anywhere along the Norwegian coast. Britain’s leaders also perhaps entertained the hopes that a success might boost British morale: a raid was practically the only offensive action that Britain could take in those days when she stood alone against a continent overrun by Nazi forces. Finally, the British would be glad for any documents that they might seize.

  Preparations for the raid began late in February. The naval commander was Captain Clifford Caslon, commanding officer simultaneously of the Somali and the Sixth Destroyer Flotilla. More a staff officer than a sailor, he was very efficient. He could wiggle his ears, and his offic
ers soon learned that when he laid them flat against his head he was angry. Nevertheless, Warmington regarded Caslon as rather tender-hearted.

  Anchored at the great naval base of Scapa Flow, the Somali and four other Tribals awaited the commandos. The 500-man detachment, supported by engineers and Norwegian volunteers, arrived in the early afternoon of February 22. For a week, the naval and military officers went over the plans for the raid in minute detail. Warmington arranged for shore-to-ship communications, instructing the sailors in the use of the commandos’ radio sets. The occupants of the landing craft and their crews got to know one another. With preparations completed, the little task force of destroyers and troopships, now codenamed REBEL, got under way. At one minute after midnight, on Saturday, March 1, it passed the antisubmarine booms and the blockships and headed north.

  The target was the Lofoten Islands. This archipelago lies above the Arctic Circle just south of where the Norwegian coast turns east to top off Europe. From north to south the strip of mountainous islands angles away from the cliff-sided coastline, leaving a bay, Vestfjord, in the shape of an inverted V. Scattered near its apex were the fishing towns with the fish-oil factories. Around the tip of the southwesternmost large island swirled the Maelstrom. Though this was not the giant fatal whirlpool of legend, with Edgar Allan Poe’s “smooth, shining, and jet-black wall of water,” its powerful currents did endanger ships. Indeed, strong currents and strong winds made sailing difficult and dangerous throughout the Lofotens.

  Task force REBEL, after refueling in the Faeroes, reached what it called Point P, some 600 miles north of Scapa, at 1:30 A.M. on Monday, and turned almost due east for the 320-mile march to Point Q, at the mouth of Vestfjord. The weather favored the trip: the winds were gentle and the sea moderate to flat. The sky was overcast with low clouds, and snow showers reduced the chances of detection. The daily German meteorological flight did not spot the ships. Occasional breaks in the cloud cover permitted astronomical position fixes, which were confirmed by radio bearings taken on signals emitted by the Royal Navy submarine Sunfish, stationed near Point Q. REBEL passed Point Q a little after midnight on March 4, swung northeast, and moved up Vestfjord. At 4:30 A.M. the task force reached Point C, on the west side of the inverted V. Fifteen minutes later the light had grown strong enough for the lookouts to see the coastline. The wind was a light breeze, the sea calm, the temperature in the low twenties.

  The previous morning a German weather flight had spotted a northbound force of one cruiser and five destroyers off the waist of Norway, some 200 miles south of where REBEL then was. The Kriegsmarine’s Admiral Polar Coast had ordered “increased watchfulness” for all coastal observation stations, patrol boats, and batteries. But coastal navigation lights were not extinguished.

  By between 5:30 and 6 A.M., the Royal Navy ships heading for three of the ports to be attacked had reached their stations. The Somali, another destroyer, and one of the troop carriers continued on to the fourth and most northeasterly of the ports. They crept by the 921-foot-high hump of the island of Skraaven, to their left. Only then, in the twilight, were they seen by lookouts there. The Germans raised the alarm. The commandant of the Narvik Sea Defense Zone was warned. Coastal batteries were alerted. The Luftwaffe was asked to send bombers. A minesweeping unit that was about to go to sea was stopped. Navigation lights were belatedly turned off. Messages came in about the other destroyers. The harbor captain of Svolvaer, the principal port of the Lofotens, reported, “Destroyer in harbor; we’re leaving.” But he was captured anyway, and the Luftwaffe never arrived.

  Aboard the troop carriers, the commandos readied their equipment and climbed into their landing craft. They were to go ashore at 6:45. At 6:10, after assuring himself that the troop carrier that the Somali and another destroyer were escorting had almost reached its position for the attack, Caslon swung the Somali around and headed south to check on the activity at the other ports. Again she had to pass mile-long Skraaven, this time on her starboard. Once past the island, she could look over the water toward Svolvaer. And coming from that direction she saw, at about 6:20, a whaling trawler that had been converted into a patrol vessel by the mounting of a small gun in her bows and a heavy machine gun aft. It was the Krebs (“shrimp” in Norwegian, “crab” in German), commanded by Lieutenant Hans Kapfinger. Her usual function was probably to prevent Norwegians from sailing from the Lofotens to the Shetlands, where they could escape the occupation and join the fight against the Germans. But now, summoned by the alert, she was bravely coming out to do battle with the vastly superior forces that had invaded her domain. Caslon trained his guns on the little ship, then a little under 2 miles distant, and opened fire.

  His first shots were high and did little damage. Then, with what Warmington thought was “all the guts in the world,” the Krebs fired back at the British warship. None of her three rounds struck the Somali, but one holed a flag flying from the destroyer’s forearm, which angered Caslon. His next three shots devastated the trawler. One detonated the ready ammunition; one burst in the wheelhouse; the third exploded in the boiler room. Smoke issued from the vessel, which appeared to have gone out of control. The Somali ceased fire. Survivors were seen in the water, and the destroyer went to rescue them.

  The Somali’s No. 1, or executive officer, the second in command, was Lieutenant Henry A. Stuart-Menteth, a career officer of the Royal Navy. His former destroyer, the Hunter, had been sunk in 1940 during the Norwegian campaign; Stuart-Menteth had been wounded in the leg in the action and was unconscious when the Germans pulled him from the water. He didn’t know where he was when he came to in a hospital, but the pictures of Hitler quickly brought him to his senses. Still, he remained grateful to the Germans for having saved his life—and for leaving him behind when they temporarily quit Narvik in the face of British attacks. Now, seeing the Germans swimming in the icy Vestfjord waters and watching one man in particular struggle, he reminded himself, “They hauled me out.” He clambered down the net thrown over the ship’s side and pulled the man aboard.

  The Krebs had stranded on a low, flat, rocky islet south of Skraaven named Flesa. So the Somali left the helpless trawler there. As she steamed off, a wounded German stoker climbed onto the trawler’s deck. In the engine room he burned some of the secret papers and cipher material. Unable to help the two petty officers and two sailors who lay wounded above deck, he jumped onto Flesa.

  At 7:10 Caslon permitted radio communications, which, thanks to Warmington’s preparations, functioned excellently. Contact was immediately established with all four landing parties, and they reported that they had come ashore without opposition and were carrying out their allotted tasks. They destroyed the Lofotens Cod Boiling Plant and the Moller Medicinal Oil Plant and destroyed oil and kerosene tanks, setting fire to their contents and sending great pillars of black smoke into the clear Norwegian sky. At the same time, the other destroyers and naval demolition parties were sinking ships and taking Germans prisoner.

  The cod run in Vestfjord from February to April, and during this period thousands of fishermen come to the islands. They had left port that Tuesday morning before the extent of the British operation became clear, and as they came to see that the attack was directed against the Germans and not them, they cheered and waved Norwegian flags on the hundreds of little fishing smacks and puffers that dotted the waters around the ports.

  The Somali stood off the most southerly of the ports for a while to observe operations, then turned back to Svolvaer. As she passed Flesa, she saw that the Krebs had refloated and, still burning, was drifting to the center of the fjord. The Somali approached and saw a white flag being waved.

  Warmington, who was on the bridge, thought that the Krebs might have some useful documents and that this was a rare chance to board an enemy ship. He knew that Caslon was concerned about being tied down, so he appealed to his superior’s compassion: he proposed boarding the Krebs to save the sailors. Caslon assented.

  To save time and retain the maxim
um freedom of movement, Caslon decided against lowering his own boat or coming alongside. Instead he summoned the commandos’ Norwegian interpreter. Second Lieutenant Leonard M. Harper-Gow, a tall, imposing former member of Scotland’s Ayrshire Yeomanry, had learned the language during summers in Norway. He was below, sulking because he had not been allowed ashore for the action; the communications were excellent and it was better for him to be at sea and mobile than fixed on land. Topside, he hailed a Norwegian fishing boat with “Halloo! Halloo!” When it came alongside, he explained what he wanted it to do. The skipper agreed, and at 9:10 Warmington, Harper-Gow, and another officer, Major A. R. Aslett, were ferried over to the Krebs.

  She was still smoldering. In the wreckage of the wheelhouse, they found four or five bodies, including that of the captain, Kapfinger, next to the wheel. Five sailors cowered on deck; two were badly wounded, one having lost a lot of muscle in his arm, the other hit in the head.

  Aslett flourished his service revolver and Warmington his own cocked Belgian pistol (the navy did not issue regulation handguns). The five men offered no resistance. Warmington put his pistol into the duffel coat he was wearing and hastily looked around. He found no signal books or codebooks and no cipher devices; evidently they had been jettisoned before the Somali’s shell struck the wheelhouse. He did find a pair of binoculars, which he liberated. Harper-Gow kept Kapfinger’s cap; someone pinched the range finder. The Krebs was still burning below, and no one could enter the engine room or the forepeak. But in the captain’s cabin Warmington found the Kriegsmarine’s gridded chart of European waters from Iceland to Norway, some personal papers, and a variety of documents, some of which appeared to be secret. All these he swept up. The other two Britons grabbed other papers. Then, in going through the drawers, Warmington found one locked.